Exemplary embodiments relate to a nonvolatile memory device and a program method thereof.
There is an increasing demand for nonvolatile memory devices which may be electrically programmed and erased without a refresh function of rewriting data at specific intervals.
Each of the memory cells of the nonvolatile memory device is an electrically programmable and erasable element.
The program and erase functions of the memory cell are performed in such a way that electrons within a thin oxide layer, e.g., about 100 Å in thickness, are moved by a strong electric field supplied to the oxide layer, thereby shifting the threshold voltages of the memory cell.
In the programming method of the nonvolatile memory device, various forms of interference phenomena are caused in a memory cell by shift in the threshold voltages of adjacent memory cells. In particular, in a multi-level cell (MLC) program method capable of storing data of 2 bits or more in one cell, a malfunction due to the interference phenomena may more frequently occur because a margin between the threshold voltages for the stored data is narrowed.